Saving on Heating and Cooling

Advice for those concerned about energy efficiency.

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Q: I'm building a home and have a few questions.

Why do the heat registers have to be by a window or door? This will interfere with the placement of our furniture.

In the underfloor crawl space, the walls are insulated, but the ends of the floor joists are not. Do I need to insulate between the joists?

Finally, should the ductwork in the crawl space be insulated?

As you can see, I am concerned about energy efficiency and want to do things right to save on heating and cooling. — B.W., Seymour, Ind.

A: Cold air at a window or a door opening needs to be tempered and circulated to properly heat the home. Placing the register near these openings circulates the heated air from the furnace up the walls, past the windows or doors and across the ceiling to the cold-air return grill. If the register is offset from the cold areas, heating the room may be more difficult. Also, placing furniture over a register will cause reduced airflow to the room, which can make the room cooler and place a burden on the furnace as it attempts to heat the home.

Work with a heating professional on proper placement of registers. Offsetting the registers may mean upgrading the heating system or having to add a zone for the rooms in question. Zoning adds a thermostat and an automatic baffling system for a particular section of the home so it can be heated or cooled independently of the rest of the home.

In Indiana, it is an energy requirement that the ends of floor joists, commonly referred to as band joists, be insulated. This is a simple matter of stuffing the cavity with friction-fit fiberglass batt insulation.

Floor joists are set 16 inches on center, which leaves a 14-1/2-by-10-inch cavity between each joist. Fiberglass wall insulation can be purchased in rolls that are 16 inches wide, 8 feet long and 3-1/2 inches thick. Cut the rolls to make 10-inch-long pieces, placing the pieces in a large plastic trash bag. Drag the bag into the crawl space and simply stick a piece of insulation into each cavity. The insulation will be held in place by friction.

Where the floor joist runs the length of the wall, attach a whole roll of fiberglass using nails or staples. Wear eye protection, a long-sleeved shirt, gloves and a protective mask when working with any type of insulation.

Ductwork located in unconditioned areas such as the attic, under floor crawl spaces or in garages needs to be sealed at each joint and each register take-off joint to prevent air leaks. Metallic tape or a duct mastic can be used to seal openings.

Ducts in attics should be insulated against heat buildup in summer. Ducts in the crawl space that suffer from condensation in summer should also be insulated. Because of the possibility of mold spore growth, the insulation should be on the outside of the ducts.

Talk to your builder and your local building official to see what is required in your area. Although local and state codes may vary, I would strongly recommend that ducts be insulated and sealed to conserve energy and promote proper airflow.

(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors.)

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